Carbon fiber mat and carbon film or paper are used in several specialized applications, such as in high-strength or abrasion-resistant structural composites, electromagnetic shielding, filtration materials, and electrodes. Because of the desirable physical properties of carbon fiber, there is a growing desire to expand the applications of carbon fiber mat and carbon paper beyond these specialized applications.
However, carbon fiber mat and carbon paper are currently cost-prohibitive when considered for high-volume mainstream applications. The reason for the high cost is primarily due to the cost of precursor, as well as the laborious and complex methods used for producing carbon fiber mat and carbon films or paper.
Mats made of carbon fiber (e.g., carbon nanotubes) are typically produced by, for example, vapor phase methods, or by extrusion or spinning (e.g., melt or electrospinning) of a carbon fiber precursor (e.g., polyacrylonitrile, i.e., PAN, or pitch) followed by carbonization. These methods are generally time and energy intensive, and thus, generally unsuited for large-scale production. Moreover, although thermally bonded non-woven mats made from PAN type precursors are known in the literature (e.g., Walker R. A., et al., “Carbon mats from melt-spun polyacrylonitrile-based precursors for automotive composites” Plastic Rubbers and Composites, 35(6/7), 242-246 (2006)), such processing generally entails diffusion-controlled oxidative stabilization of the precursors mats. However, oxidative stabilization of PAN fibers is a demanding and complex process, and thus, difficult to integrate into a large-scale industrial process, specifically for thick bundles of filaments in felt or bonded mat form that is neither woven nor knitted.